text: import os
  import time
  import stat
  
  from testutils import assert_raises
  
  fd = os.open('README.md', os.O_RDONLY)
  assert fd > 0
  
  os.close(fd)
  assert_raises(OSError, lambda: os.read(fd, 10))
  assert_raises(FileNotFoundError, lambda: os.open('DOES_NOT_EXIST', os.O_RDONLY))
  assert_raises(FileNotFoundError, lambda: os.open('DOES_NOT_EXIST', os.O_WRONLY))
  assert_raises(FileNotFoundError, lambda: os.rename('DOES_NOT_EXIST', 'DOES_NOT_EXIST 2'))
  
  try:
  	os.open('DOES_NOT_EXIST', 0)
  except OSError as err:
  	assert err.errno == 2
  
  
  
  assert os.O_RDONLY == 0
  assert os.O_WRONLY == 1
  assert os.O_RDWR == 2
  
  ENV_KEY = "TEST_ENV_VAR"
  ENV_VALUE = "value"
  
  assert os.getenv(ENV_KEY) == None
  assert ENV_KEY not in os.environ
  assert os.getenv(ENV_KEY, 5) == 5
  os.environ[ENV_KEY] = ENV_VALUE
  assert ENV_KEY in os.environ
  assert os.getenv(ENV_KEY) == ENV_VALUE
  del os.environ[ENV_KEY]
  assert ENV_KEY not in os.environ
  assert os.getenv(ENV_KEY) == None
  
  if os.name == "posix":
  	os.putenv(ENV_KEY, ENV_VALUE)
  	os.unsetenv(ENV_KEY)
  	assert os.getenv(ENV_KEY) == None
  
  assert os.curdir == "."
  assert os.pardir == ".."
  assert os.extsep == "."
  
  if os.name == "nt":
  	assert os.sep == "\\"
  	assert os.linesep == "\r\n"
  	assert os.altsep == "/"
  	assert os.pathsep == ";"
  else:
  	assert os.sep == "/"
  	assert os.linesep == "\n"
  	assert os.altsep == None
  	assert os.pathsep == ":"
  
  assert os.fspath("Testing") == "Testing"
  assert os.fspath(b"Testing") == b"Testing"
  assert_raises(TypeError, lambda: os.fspath([1,2,3]))
  
  class TestWithTempDir():
  	def __enter__(self):
  		if os.name == "nt":
  			base_folder = os.environ["TEMP"]
  		else:
  			base_folder = "/tmp"
  		name = os.path.join(base_folder, "rustpython_test_os_" + str(int(time.time())))
  		os.mkdir(name)
  		self.name = name
  		return name
  
  	def __exit__(self, exc_type, exc_val, exc_tb):
  		# TODO: Delete temp dir
  		pass
  
  
  class TestWithTempCurrentDir():
  	def __enter__(self):
  		self.prev_cwd = os.getcwd()
  
  	def __exit__(self, exc_type, exc_val, exc_tb):
  		os.chdir(self.prev_cwd)
  
  
  FILE_NAME = "test1"
  FILE_NAME2 = "test2"
  FILE_NAME3 = "test3"
  SYMLINK_FILE = "symlink"
  SYMLINK_FOLDER = "symlink1"
  FOLDER = "dir1"
  CONTENT = b"testing"
  CONTENT2 = b"rustpython"
  CONTENT3 = b"BOYA"
  
  with TestWithTempDir() as tmpdir:
  	fname = os.path.join(tmpdir, FILE_NAME)
  	fd = os.open(fname, os.O_WRONLY | os.O_CREAT | os.O_EXCL)
  	assert os.write(fd, CONTENT2) == len(CONTENT2)
  	os.close(fd)
  
  	fd = os.open(fname, os.O_WRONLY | os.O_APPEND)
  	assert os.write(fd, CONTENT3) == len(CONTENT3)
  	os.close(fd)
  
  	assert_raises(FileExistsError, lambda: os.open(fname, os.O_WRONLY | os.O_CREAT | os.O_EXCL))
  
  	fd = os.open(fname, os.O_RDONLY)
  	assert os.read(fd, len(CONTENT2)) == CONTENT2
  	assert os.read(fd, len(CONTENT3)) == CONTENT3
  	os.close(fd)
  
  	fname3 = os.path.join(tmpdir, FILE_NAME3)
  	os.rename(fname, fname3)
  	assert os.path.exists(fname) == False
  	assert os.path.exists(fname3) == True
  
  	fd = os.open(fname3, 0)
  	assert os.read(fd, len(CONTENT2) + len(CONTENT3)) == CONTENT2 + CONTENT3
  	os.close(fd)
  
  	os.rename(fname3, fname)
  	assert os.path.exists(fname3) == False
  	assert os.path.exists(fname) == True
  
  	# wait a little bit to ensure that the file times aren't the same
  	time.sleep(0.1)
  
  	fname2 = os.path.join(tmpdir, FILE_NAME2)
  	with open(fname2, "wb"):
  		pass
  	folder = os.path.join(tmpdir, FOLDER)
  	os.mkdir(folder)
  
  	symlink_file = os.path.join(tmpdir, SYMLINK_FILE)
  	os.symlink(fname, symlink_file)
  	symlink_folder = os.path.join(tmpdir, SYMLINK_FOLDER)
  	os.symlink(folder, symlink_folder)
  
  	names = set()
  	paths = set()
  	dirs = set()
  	dirs_no_symlink = set()
  	files = set()
  	files_no_symlink = set()
  	symlinks = set()
  	for dir_entry in os.scandir(tmpdir):
  		names.add(dir_entry.name)
  		paths.add(dir_entry.path)
  		if dir_entry.is_dir():
  			assert stat.S_ISDIR(dir_entry.stat().st_mode) == True
  			dirs.add(dir_entry.name)
  		if dir_entry.is_dir(follow_symlinks=False):
  			assert stat.S_ISDIR(dir_entry.stat().st_mode) == True
  			dirs_no_symlink.add(dir_entry.name)
  		if dir_entry.is_file():
  			files.add(dir_entry.name)
  			assert stat.S_ISREG(dir_entry.stat().st_mode) == True
  		if dir_entry.is_file(follow_symlinks=False):
  			files_no_symlink.add(dir_entry.name)
  			assert stat.S_ISREG(dir_entry.stat().st_mode) == True
  		if dir_entry.is_symlink():
  			symlinks.add(dir_entry.name)
  
  	assert names == set([FILE_NAME, FILE_NAME2, FOLDER, SYMLINK_FILE, SYMLINK_FOLDER])
  	assert paths == set([fname, fname2, folder, symlink_file, symlink_folder])
  	assert dirs == set([FOLDER, SYMLINK_FOLDER])
  	assert dirs_no_symlink == set([FOLDER])
  	assert files == set([FILE_NAME, FILE_NAME2, SYMLINK_FILE])
  	assert files_no_symlink == set([FILE_NAME, FILE_NAME2])
  	assert symlinks == set([SYMLINK_FILE, SYMLINK_FOLDER])
  
  	# Stat
  	stat_res = os.stat(fname)
  	print(stat_res.st_mode)
  	assert stat.S_ISREG(stat_res.st_mode) == True
  	print(stat_res.st_ino)
  	print(stat_res.st_dev)
  	print(stat_res.st_nlink)
  	print(stat_res.st_uid)
  	print(stat_res.st_gid)
  	print(stat_res.st_size)
  	assert stat_res.st_size == len(CONTENT2) + len(CONTENT3)
  	print(stat_res.st_atime)
  	print(stat_res.st_ctime)
  	print(stat_res.st_mtime)
  	# test that it all of these times are greater than the 10 May 2019, when this test was written
  	assert stat_res.st_atime > 1557500000
  	assert stat_res.st_ctime > 1557500000
  	assert stat_res.st_mtime > 1557500000
  
  	stat_file2 = os.stat(fname2)
  	print(stat_file2.st_ctime)
  	assert stat_file2.st_ctime > stat_res.st_ctime
  
  	# wait a little bit to ensures that the access/modify time will change
  	time.sleep(0.1)
  
  	old_atime = stat_res.st_atime
  	old_mtime = stat_res.st_mtime
  
  	fd = os.open(fname, os.O_RDWR)
  	os.write(fd, CONTENT)
  	os.fsync(fd)
  
  	# wait a little bit to ensures that the access/modify time is different
  	time.sleep(0.1)
  
  	os.read(fd, 1)
  	os.fsync(fd)
  	os.close(fd)
  
  	# retrieve update file stats
  	stat_res = os.stat(fname)
  	print(stat_res.st_atime)
  	print(stat_res.st_ctime)
  	print(stat_res.st_mtime)
  	if os.name != "nt":
  		# access time on windows has a resolution ranging from 1 hour to 1 day
  		# https://docs.microsoft.com/en-gb/windows/desktop/api/minwinbase/ns-minwinbase-filetime
  		assert stat_res.st_atime > old_atime, "Access time should be update"
  		assert stat_res.st_atime > stat_res.st_mtime
  	assert stat_res.st_mtime > old_mtime, "Modified time should be update"
  
  	# stat default is follow_symlink=True
  	os.stat(fname).st_ino == os.stat(symlink_file).st_ino
  	os.stat(fname).st_mode == os.stat(symlink_file).st_mode
  
  	os.stat(fname, follow_symlinks=False).st_ino == os.stat(symlink_file, follow_symlinks=False).st_ino
  	os.stat(fname, follow_symlinks=False).st_mode == os.stat(symlink_file, follow_symlinks=False).st_mode
  
  	# os.path
  	assert os.path.exists(fname) == True
  	assert os.path.exists("NO_SUCH_FILE") == False
  	assert os.path.isfile(fname) == True
  	assert os.path.isdir(folder) == True
  	assert os.path.isfile(folder) == False
  	assert os.path.isdir(fname) == False
  
  	assert os.path.basename(fname) == FILE_NAME
  	assert os.path.dirname(fname) == tmpdir
  
  	with TestWithTempCurrentDir():
  		os.chdir(tmpdir)
  		assert os.getcwd() == os.path.realpath(tmpdir)
  		os.path.exists(FILE_NAME)
  
  # supports
  assert isinstance(os.supports_fd, set)
  assert isinstance(os.supports_dir_fd, set)
  assert isinstance(os.supports_follow_symlinks, set)
  